The goal of this project is the prevention or control of trachoma, the world's most important cause of blindness, and of other diseases caused by infection with trachoma and closely related organisms. The goal is sought through better understanding of the pathogenesis, immunology and epidemiology of trachoma and the related diseases and through studies of the trachoma-LGV organisms. Field investigations of trachoma and of eye and genital tract infections with trachoma and related organisms will be carried out both in Taiwan and in the United States. A microimmunoflurescence test which measures type specific antibody in serum and eye secretions will be utilized in these field studies of pathogenesis. Studies of the organisms will be directed at improved immunoclassification, determination of biological characteristics and the isolation and chemical description of their antigens. The monkey eye trachoma model will be used for studies will newly described group and specific antigens, allergens, and toxins in order to determine their role in the pathogenesis of he disease. The role of a genital reservoir for trachoma organisms will be evaluated in areas of trachoma endemicity on Taiwan, in areas no longer endemic for trachoma on Taiwan and in the United States. Bibliographic references: Wang, S.P., Grayston, J.T., Alexander, E.R., and Holmes, K.K: Simplififed microimmunofluorescence test with Trachoma-LGV (Chlamydia trachomatis) antigens for use as a screening test for antibody. J. Clin. Microbiol. 1:250-255, 1975. Grayston, J.T. and Wang, S.P.: New knowledge of chlamydise and the diseases they cause. J. Infect. Dis. 132:87- 105, 1975.